花櫻
・・・・・櫻 is an old kanji. Some use it in their names though, we usually prefer 桜, which is a modern version.
Anyway, はなさくら, or はなざくら, right? Either will do. Sounds very good.

微風上浮流
・・・・・Ok. There is a minor problem.
Well.. Hundreds of years ago in Japan, they used Chinese when they write something. Because kanji was originally created in China and Japan only imported them. The big difference between "Chinese origin writing" and "pure Japanese writing" is a difference of "yomi", how to pronounce it, ok?
微風上浮流 can be pronounced like びふうじょうふりゅう in our MODERN Japanese.
But in our archaic way of Chinese origin literature allows us to read it as...like... そよかぜのうえにうきながれ.
So, in a way, for us average Japanese, it is virtually impossible to make out how we should "pronounce" your line.
And, the genre is also important here. Because, if you are trying to create a kind of "Chinese origin poem" (like 五言絶句), your style totally makes sense. However, as you wrote, you are creating Haiku, right? Haiku is supposed to be pure Japanese style. (at least today) So, it would be better to use Hiragana as well. Like.... 風に流れる（かぜにながれる-7） or 風に運ばれる（かぜにはこばれる-8...Yes, it is true that there is some latitude with the mora） or そよ風に浮く（そよかぜにうく-7）.

優しい春
・・・・・やさしいはる. Good.

Maybe it would be confusing that we have many styles in our traditional literature. Actually you could find many Haiku written in only kanji like Chinese poems. But usually we avoid the style when we make something new today. (Unless you are an expert in the field)

Anyway, I liked your image in your haiku. Your concept is absolutely beautiful and seems to be very decent as haiku.
Good work!

I can't remember why i chose 櫻 instead of 桜. I've certainly run into the latter in my reading, never the former. I can't say I was looking for an "old" style because I wouldn't know the difference. I sometimes wonder if the 万葉集 or 源氏物語 are for modern Japanese what The Canterbury Tales or The Faerie Queen are for modern English: archaic and abstruse.

When I wrote 微風上浮流, I remember I had the modern reading in mind. I like your third fix.

I thoroughly enjoyed by Sansome's Historical Grammar (it's the source of the quote in my signature). I'd love to find more material like it.

I'm kind of curious that if you've ever learned Chinese.
For instance, "心為花" definitely seems Chinese expression to me. Although, as I mentioned, it's difficult to differentiate Chinese and Japanese in the histrical context. In fact, in the middle ages, Japanese intelligentsiya prefered using Chinese rather than Japanese. Because most of our literature came from that advanced country in the era. Hey, take a look at the world atlas. China is a huge country which had one of the oldest civilization in the world. Compared to that, Japan looks like a flyspeck.
Then thing is, you can't expect us ordinary Japanese people to be able to read histrical usage of Chinese expressions today.
Also, strictly speaking, the language used in 万葉集, which was conceived in 8th century, is considerably different from the one used in 源氏物語, which was written in 11th century. Well, honestly, I know next to nothing about the details though. That's at least what I learned at school a million years ago.

BTW, thanks becki!
Although I knew that 季語 is crucial in haiku, I hadn't heard the term 切れ字 for decades since I graduated from school. Pardon my...French

It was late at night when I wrote it, so I used 深更 for "midnight"
燃し為- I used the participle to fit the meter; I didn't use ため for some rather indelicate alternate translations (ために wouldn't have fit).
I used 愛 instead of 恋 to fit the beat better; I think I might have committed the sin of carrying a thought to the next line, too.
厚 instead of 厚い was kind an elision, but "thickness" isn't what I intended.
Oh well, it's still a fun exercise.

"心為花"-from G. B. Sansom's "An Historical Grammar of Japanese". http://www.archive.org/stream/historica ... 2/mode/2up He didn't cite the source, and I haven't yet found it among the works at the U. of Virginia Etext site. It's in romaji, so I had to best-guess the kana. The second line is my own, so I used modern language to avoid an artificial gravitas.